Spheroidal textures in igneous rocks – Textural consequences of H2O saturation in basaltic melts
Spheroidal textures in igneous rocks – Textural consequences of H2O saturation in basaltic melts
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DOI：
10.1016/j.gca.2015.07.029
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发表时间：
2015-10
影响因子：
5
通讯作者：
C. Ballhaus;R. Fonseca;C. Münker;M. Kirchenbaur;Aurelia Zirner
中科院分区：
文献类型：
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作者：
C. Ballhaus;R. Fonseca;C. Münker;M. Kirchenbaur;Aurelia Zirner
当熔体到达H2O饱和之前，它们被安置在地球表面，它们exsolve含水流体相。在高压和高温下，含水流体不是纯的H2O，而是可以含有一定量的硅酸盐和金属氧化物溶质，特别是如果流体饱和发生在高压下。在化学和物理上，流体饱和的玄武岩表现得像任何其他具有液体不可渗透性的系统。在固化之后可以产生的纹理是分散在前硅酸盐熔体中的前流体的小球，或者嵌入前流体基质中的硅酸盐熔体球体。塞浦路斯岛上的Troodos蛇绿岩产于潮湿的洋内俯冲带之上的弧后盆地中，其岩浆地层岩性具有明显的圆形和球形。许多熔融组合物父母的蛇绿岩是H2O饱和的液相线温度附近之前，他们到达他们的深度侵位的蛇绿岩序列。球状体在岩浆岩中并不罕见，但关于它们是如何形成的仍然存在争议。我们建议，在全球范围内的火成岩球状和球状纹理可能会导致熔体达到H2O饱和度和exsolve一个不混溶的溶质轴承H2O为主的流体相在升高的温度和压力，之前或同时，他们被安置。
When melts reach H2O saturation before they are emplaced at the Earth’s surface, they exsolve a hydrous fluid phase. At elevated pressure and high temperature, a hydrous fluid is not pure H2O but can contain some quantities of silicate and metal oxide solute, notably if fluid saturation occurs at high pressure. Chemically and physically, fluid-saturated basalts behave like any other system with liquid immiscibility. Textures that can result after solidification are globules of former fluid dispersed in a former silicate melt, or silicate melt orbs embedded in a former fluid matrix. The Troodos ophiolite on the island of Cyprus, generated in a back arc basin above a wet intra oceanic subduction zone, carries in its magmatic stratigraphy lithologies distinctly orbicular and globular in shape. Many melt compositions parental to the ophiolite were H2O-saturated near their liquidus temperatures before they reached their depths of emplacement within the ophiolite sequence. Spheroids are not uncommon in magmatic rocks but still debated as to how they form. We propose that globular and orbicular textures in igneous worldwide may result when melts reach H2O saturation and exsolve an immiscible solute-bearing H2O-dominated fluid phase at elevated temperature and pressure, before or while they are emplaced.